"Conditions in the tropical Atlantic look quite favorable for an active hurricane season," CSU forecaster Phil Klotzbach said in a prepared statement.

Klotzbach and CSU colleague William Gray think a total of 15 tropical storms will form in the Atlantic Basin, which includes the Caribbean Sea and the Gulf of Mexico (see map).

Tropical Storm Arthur, the season's first, came ashore Saturday along the Mexico-Belize border.

Although the storm was weakening as it made landfall, heavy rains triggered flash floods that swept away houses and wiped out bridges, according to the Associated Press.

Arthur has since been downgraded to a tropical depression.

East Coast Landfall?

Hurricanes draw their energy from warm waters, and Klotzbach said this year's unusually warm sea-surface temperatures—along with the absence of upper-level winds known to inhibit storm formation—could contribute to an active season.

Long-term yearly averages are nine or ten named storms, six of which are hurricanes, and two of which are intense hurricanes.

In April the CSU forecasters had said there is a 70 percent likelihood that a major hurricane will make landfall somewhere on the U.S. East Coast.

But they did not speculate about where the hurricane is likely to come ashore.